On June 30, a 47-year-old man was hospitalized with dizzines…

On June 30, a 47-year-old man was hospitalized with dizziness, blurred vision, slurred speech, difficulty swallowing, and nausea. Examination revealed facial paralysis. The patient had partially healed superficial knee wounds incurred while laying cement. He reported eating home-canned mushrooms and stew containing roast beef and potatoes 24 hours before onset of symptoms. Which of the following is true?